Conventional fibers are useful in a variety of applications including reinforcements, textiles, and acoustical and thermal insulation materials. Although mineral fibers (e.g., glass fibers) are typically used in insulation products and non-woven mats, depending on the particular application, organic fibers such as polypropylene, polyester, and multi-component fibers may be used alone or in combination with mineral fibers in conning the insulation product or non-woven mat.
Fibrous insulation is typically manufactured by fiberizing a molten composition of polymer, glass, or other mineral and spinning fine fibers from a fiberizing apparatus, such as a rotating spinner. To form an insulation product, fibers produced by the rotating spinner are drawn downwardly from the spinner towards a conveyor by a blower. As the fibers move downward, a binder material is sprayed onto the fibers and the fibers are collected into a high loft, continuous blanket on the conveyor. The binder material gives the insulation product resiliency for recovery after packaging and provides stiffness and handleability so that the insulation product can be handled and applied as needed in the insulation cavities of buildings. The binder composition also provides protection to the fibers from interfilament abrasion and promotes compatibility between the individual fibers.
The blanket containing the binder-coated fibers is then passed through a curing oven and the binder is cured to set the blanket to a desired thickness. After the binder has cured, the fiber insulation may be cut into lengths to form individual insulation products, and the insulation products may be packaged for shipping to customer locations. One typical insulation product produced is an insulation batt or blanket, which is suitable for use as wall insulation in residential dwellings or as insulation in the attic and floor insulation cavities in buildings. Another common insulation product is air-blown or loose-fill insulation, which is suitable for use as sidewall and attic insulation in residential and commercial buildings as well as in any hard-to-reach locations. Loose-fill insulation is formed of small cubes that are cut from insulation blankets, compressed, and packaged in bags.
Non-woven mats may be formed by conventional wet-laid processes. For example, wet chopped fibers are dispersed in a water slurry that contains surfactants, viscosity modifiers, defoaming agents, and/or other chemical agents. The slurry containing the chopped fibers is then agitated so that the fibers become dispersed throughout the slurry. The slurry containing the fibers is deposited onto a moving screen where a substantial portion of the water is removed to form a web. A binder is then applied, and the resulting mat is dried to remove any remaining water and cure the binder. The formed non-woven mat is an assembly of dispersed, individual glass filaments.
Various attempts have been made to reduce undesirable formaldehyde emissions from formaldehyde-based resins. For example, various formaldehyde scavengers such as ammonia and urea have been added to the formaldehyde-based resin in an attempt to reduce formaldehyde emission from the insulation product. Because of its low cost, urea is added directly to the uncured resin system to act as a formaldehyde scavenger. The addition of urea to the resin system produces urea-extended phenol-formaldehyde resole resins. These resole resins can be further treated or applied as a coating or binder and then cured. Unfortunately, the urea-extended resoles are unstable, and because of this instability, the urea-extended resoles must be prepared on site. In addition, the binder inventory must be carefully monitored to avoid processing problems caused by undesired crystalline precipitates of dimer species that may form during storage. Ammonia is not a particularly desirable alternative to urea as a formaldehyde scavenger because ammonia generates an unpleasant odor and may cause throat and nose irritation to workers. Further, the use of a formaldehyde scavenger in general is undesirable due to its potential adverse affects to the properties of the insulation product, such as lower recovery and lower stiffness.
In addition, previous arts have focused on the use of polyacrylic acid with a polyhydroxy crosslinking agent or carbohydrate-based chemistry that is linked to the Maillard reaction. A binder that is formed mostly of polyacrylic acid inherently has problems due to its acidity and associated corrosion of machine parts. In addition, polyacrylic acid binders have a high viscosity, high curing temperatures, and high associated curing costs. Further, the Maillard-based products have an undesirable dark brown color after curing. Also, the use of large amounts of ammonia needed to make the binder presents a safety risk and possible emission problems.
Alternative polymeric binder systems to those described above for fibrous glass products have also been proposed. However, these alternative binder systems remain problematic. For example, low molecular weight, low viscosity binders which allow maximum vertical expansion of the insulation pack in the transfer zone generally cure to form a non-rigid plastic matrix in the finished product, thereby reducing the attainable vertical height recovery of the finished insulation product when installed. Conversely, high viscosity binders, which generally cure to form a rigid matrix in the finished product, do not allow the desired maximum vertical expansion of the coated, uncured pack.
In view of the existing problems with current binders, there remains a need in the art for a binder system that does not corrode machine parts, does not emit formaldehyde, and which is environmentally friendly.